Automated Teller Machines (ATMs) may be utilized to provide services in addition to the conventional one of supplying currency. For example, ATMs may allow users to pay bills. To enable this, certain information relating to the bill to be paid must be transferred to the ATM, for example the company to whom payment should be made and the amount to be paid. That information could be entered by the user, but a more convenient method is to read a barcode containing that information printed on the bill. The use of automated barcode reading simplifies the process for users and enables ATM machines to provide an improved service to their customers.
Barcodes are machine-readable patterns formed of contrasting areas which represent information. Common forms of barcodes may contain information in either one dimension or two dimensions. Single dimensional barcodes are formed of a set of parallel lines of varying width and spacing, which width and spacing encodes information into the barcode. Two dimensional barcodes are generally square or rectangular in outline and contain a pattern of contrasting areas which represent the information.
A convenient method of reading single-dimensional barcodes is to scan a narrow light source, for example a laser beam across the barcode, and to detect the lines of contrast as the beam moves across the barcode. This is the method commonly used in commercial barcode reading apparatus, for example those used in shop point of sale systems for reading barcodes on products. Two dimensional barcodes cannot be read using this laser technique as it is not, possible to scan the beam over the code in a sufficiently simple manner to obtain all of the required information.
An alternative technique of reading barcodes is to capture a digital image of the barcode using, for example, a CCD array, and process that image to identify the barcode area and decode the information represented by the barcode. This technique allows two dimensional barcodes to be read, but relies upon the ability to acquire a sufficiently detailed and illuminated image of the barcode.
A requirement of reading barcodes by processing an image is that the illumination over the area of the barcode is relatively constant, and in particular that there are no sharp changes in illumination over the area of the barcode. Such sharp changes can result in the confusion of lines in the barcode with the change in illumination thereby preventing correct decoding. Furthermore, a change in illumination across the barcode, combined with limitations in the contrast capability of the CCD, may prevent a sufficiently clear image being obtained of the whole barcode. For example, the area of the barcode with higher illumination may be washed out when the exposure is correct for the less illuminated part, and vice-versa. Scanning laser-based readers do not suffer from this problem since the light source is sufficiently bright to overcome any ambient light.
In order for automated reading of barcodes to be feasible, the read accuracy must be very high, and must be sufficiently simple to use that users can easily make use of the facility. Furthermore, since ATMs are located in uncontrolled environments, they must meet all relevant safety standards for apparatus accessible by the public. The use of laser-based barcode readers is therefore restricted as the bright light source of the laser is a safety hazard. Barcode readers in ATMs therefore utilize the image processing method.
ATMs may be located both indoors and outside, and therefore under both artificial and natural light of widely varying intensity. Furthermore, the illumination across a barcode can vary significantly due to shadows being cast across the barcode, for example due to the user's shadow falling on part of the barcode. The variation in illumination may be such that conventional CCD reading systems cannot read barcodes in all conditions, which is not acceptable as the services provided by ATMs must be operable the vast majority of the time.
The reading of barcodes by an ATM is a relatively unique problem since the system is subject to restrictions on the type of reader that can be used, and also the environment in which the ATM is located is almost totally uncontrolled. There is therefore a requirement for an improved barcode reading system capable of reading barcodes in a wide variety of lighting environments.
There are also practical considerations and problems which arise in implementing a light source suitable for the aforementioned barcode imaging system. In particular, while the IR illumination improves the read performance of barcodes on certain materials, barcodes on other materials are read more successfully without the illumination. For example, if the barcode is provided on thermal paper the IR illumination may degrade the image and cause reading of the barcode to be more difficult.
In addition, the LEDs in the illumination array are high brightness and narrow beam angle and are therefore subject to LASER safety legislation. The LEDs can not exceed LASER class 1 safety limits and it is a further requirement of this legislation is that the system will remain within the safety limits even under a single component failure condition.